This invention relates to a combustor unit for a woodburning stove. More particularly, this invention relates to a combustor unit which employs a member having a catalyst for facilitating combustion of exhaust gases from a woodburning stove.
The increased popularity of woodburning stoves has reawakened interest in a number of the problems associated with the burning of wood. A critical problem in the use of woodburning stoves is the production of creosote and other pollutants resulting from the burning of wood. The build-up of creosote in the exhaust flues and chimneys of woodburning stoves produces an unpleasant odor, a potential for seepage from the exhaust conduits and, most of all, presents a potential for combustion and ultimately an uncontrolled fire. In addition to the safety and sanitary hazards presented by the burning of wood, increased emphasis has been directed to energy conversion, e.g., the obtaining of the largest quantity of useful heat from each unit of fuel.
The foregoing problems associated with woodburning stoves have been addressed by the employment of a combustor member in the path of the exhaust gases produced by a woodburning stove. Such combustor members typically are comprised of a ceramic porous material with a surface consisting of a noble metal catalyst. The combustor units function in a well-known and conventional manner by providing a catalyst wherein combustible materials in the exhaust gases, and in particular creosote forming gases, are ignited at a relatively low temperature, conventionally on the order of 500 degrees F. to 2000 degrees F., the heat generated by the woodburning stove being sufficient to ignite the exhaust gases.
While the use of such catalytic combustor units has proved useful in eliminating substantial quantities of creosote and in increasing the efficiency of the woodburning stove, there have previously been a number of limitations in the use of such catalytic combustors. For example, such catalytic combustor units over a period of operation become sites for the deposits of carbon ash residue and creosote residue. The carbon ash residue may be deposited on the combustor in such a manner that the combustor element is clogged and eventually becomes inoperative. The creosote residue may also clog the catalytic combustor over a period of time and prevent or interfere with proper functioning of the combustor unit. In order to repair or clean the combustor member, it has heretofore generally been necessary to remove the combustor member which removal usually requires disassembly of the exhaust flue. An additional problem associated with ceramic-type catalytic combustors is that these combustors are very susceptible to damage from thermal shock and flame impingement. If the combustor is exposed to colder air currents during the operation interval at approximately 500 degrees F. to 2000 degrees F. (such as by opening the door of the stove to add wood or opening the air vents), the combustor can be severely damaged. Flame impinging on a combustor having a porous ceramic substrate can burn a hole through the substrate. In addition, it is well known that the combustion of non-wood fuel such as coal, kerosene, treated wood, painted wood, oil based starters, and artificial logs will "poison" a combustor in the exhaust gas path from such materials by rendering substantial portions or all of the catalytic agent inoperative.
The present invention is directed to providing a new and improved combustor unit having features which eliminate or minimize a number of the foregoing noted deficiencies relative to the incorporating of catalytic combustor units into the exhaust systems of woodburning stoves.